Pipelaying Vessel

ABSTRACT

There is disclosed a variety of arrangements for laying of rigid pipe from reeled storage and/or on-board welding fabrication. Thirteen independent aspects of the invention are identified. In one particular arrangement ( FIGS. 3   a -3 b ), a tilting lay tower ( 106 ) having two travelling clamps ( 210, 220 ) is provided centrally on a pipelay vessel with a radius control arch ( 140 ) pivotable to receive rigid pipe from either port or starboard lay paths. A vertical axis reel or carousel ( 104 ) is provided, within an arrangement of curved take-off arms ( 130, 134 ) and a large radius curved wall ( 128 ). By these means, pipe can be loaded onto the carousel either clockwise or anti-clockwise, and can be supplied to the lay tower via the port or starboard lay path. Continuous rigid product fabricated by a selection of welding lines ( 112, 114, 116 ) at the port side can be guided around the large radius wall either for reeling onto the carousel or for direct feeding to the lay tower. A stinger  110  at the starboard side can be used for on-loading of prefabricated pipe. A pipe elevator ( 150 ) can erect larger pipe stalks (double- or quad-joints) from deck level for welding within the tower. Flexible product can be stored within an inner compartment ( 1042 ) of the carousel and laid via the same tower. The vessel may be a reversible conversion of a FPSO.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application is a continuation of and claims the benefits of U.S.application Ser. No. 10/544,046, which is incorporated herein byreference for all purposes.

The present invention relates to methods and apparatus for layingelongate articles from a vessel, in particular but not limited to thelaying a variety of elongate articles such as pipe and power cable froman offshore pipelaying vessel.

There are increasing requirements in the offshore industry for laying tothe seabed a variety of different articles from a single vessel. Also,the waters in which the laying is taking place are getting deeper, andmore remote from base. If it is not possible to lay different types ofarticles with a single vessel then a number of different ones arerequired, with an obvious impact on cost and logistics. Furthermore,there are other circumstances where a single vessel is necessary, suchas laying in combination different articles, such as atelecommunications cable coupled to an oil pipeline.

Pipeline is laid either by forming a pipeline out of sections, which arewelded together on the deck of the vessel and progressively fed into thesea, or by unreeling from a spool containing flexible pipeline. Thespools have to be very large due to limitations in bend radius of thepipeline. Clearly pipeline of smaller diameter can be bent more acutely,allowing smaller reels to be used, where appropriate. Some articles areinsufficiently rigid for them to be stored in a reel, or too heavy to bestored in a large horizontal-axis reel, requiring instead storage in a“basket” that is rotated about the vertical axis.

Ideally, a single vessel would be capable of laying a variety ofdifferent types of elongate articles by reel lay, and/or basket lay.

To reduce costs further it is also desirable to maximise the amount ofmaterial carried by the vessel. However, there are mechanicallimitations on the amount that a single vertical reel (operating about ahorizontal axis) can carry. For example, the taller a vertical reel, thehigher its centre-of-gravity in the ship, and the greater the risk ofcapsize in adverse weather conditions.

To increase reel capacity safely the industry has progressed moretowards “horizontal”, vertical-axis reel-lay.

There are presently a variety of different vessels available for layingarticles on the seabed, examples of which are provided below:-

For rigid pipelay, the older vessel named “Chickasaw” uses a horizontal(vertical-axis) reel, the output of which feeds a pipe conditioningtrain and stinger, in a conventional manner. However, no provision ismade for laying flexible pipe. See, for example, U.S. Pat. No. 3,712,100and U.S. Pat. No. 3,630,461.

The vessel named “Seaway Falcon” has two separate lay systems, one forrigid, and one for flexible pipe. The flexible pipes are stored in 1500ton capacity horizontal (vertical-axis) rotating baskets below the deck,while rigid pipe is stored in discrete lengths and welded togetherbefore laying over a stern ramp. Power cable is generally laid fromlarge vertical-axis rotating baskets installed on the ship's upper deck.See U.S. Pat. No. 5,975,802 (Willis). Modifications of this generalarrangement but using travelling clamps in place of a track-typetensioner on the ramp are known from GB2364758A and GB2370335A.

The vessel named “Apache” has a single lay system comprising a vertical(horizontal-axis) reel, and a pivotable stem lay ramp. The product isunreeled and deployed in a single, vertical plane and doing soplastically deforms the pipe twice in the same direction. See, forexample, U.S. Pat. No. 4,345,855.

The more recent vessel named “Deep Blue” uses very large vertical(horizontal-axis) reels with a flange diameter of some 31 metres andcapacity of 5000 tons. It also has separate rotating baskets ofapproximately 2000 ton capacity for the stowage of flexible pipe. Thevessel uses the same lay tower for both rigid and flexible articles.However, separate track tensioners and travelling clamps are providedfor the laying of continuous product and J-lay rigid pipe, respectively,and two separate radius controllers. The reels have to be sunk deep intothe vessel to keep the centre-of-gravity low enough to allow adequatelength of pipe to be carried within the stability limitations of thevessel. See, for example, U.S. Pat. No. 6,371,694.

Accordingly, it is an object of the present invention to provideimproved methods and apparatuses for laying elongate articles from avessel, particularly using a single convertible platform with low centreof gravity and maximum versatility.

The invention in a first aspect provides a sea-going vessel having pipelaunching apparatus for laying continuous elongate product, the pipelaunching apparatus comprising:

-   -   first product supply apparatus arranged substantially at deck        level for supplying continuous elongate product into a first        path along a deck at one side of the vessel;    -   second product supply apparatus arranged substantially at deck        level for supplying continuous elongate product into a second        path along deck at the opposite side of the vessel;    -   a tower structure mounted substantially on the vessel centreline        and inclinable to a desired launch angle to align with a        catenary curve of said product suspended below the vessel;    -   pipe handling means within said tower structure operable to        receive said product at a central elevated position for gripping        and supporting the weight of the suspended product while paying        it out; and    -   tower diverter means operable for receiving said product from        deck level at one of two side elevated positions above said        first path or said second path respectively according to        whichever production apparatus is being used, and for supporting        the product in a curved path from the side elevated position to        said central elevated position and aligning it with said launch        angle.

It will be seen from the following summary and from the detailedembodiments which are described herein, that such an arrangementprovides unprecedented versatility in choice of operational modes andproduct types. It will be seen from what follows that an individualcomponent such as a carousel or welding line can serve at differenttimes as part of both the first and the second production apparatus. Toease understanding, therefore, it should be noted that the “first path”and “second path” mentioned above may be just short segments of anoverall path of the product on each side, which may be convoluted inpractice, and will vary according to the many possible modes ofoperation. In the terms of this aspect of the invention, however, theseparticular segments are used to define which of the first and second“production apparatus” is being used. The same could be explained indifferent terms by viewing one such component as a part of only thefirst or the second production apparatus, and explaining the differentpaths as features of different modes of operation. The choice of oneparticular terminology is merely for defining the invention clearly andconsistently, and does not imply any limitation on the scope of theinvention compared with any other choice of terminology.

Said first product supply apparatus may include at least one pipelineproduction facility for receiving sections of rigid pipe and joiningthem to produce said continuous product for supply directly to said pipehandling means via said first path. In a preferred embodiment, analternative production facility for a different process is arranged inparallel, on a deck above the other. One is rapid but inflexible, whilethe other is adaptable to a wider range of products.

Said pipeline production facility may be arranged toward the oppositeside of the vessel from said first path and anti-parallel thereto, theproduct being diverted through a 180° curved path into said first pathand thence to the tower diverter. It goes without saying that strictcompliance with terms such as “anti-parallel” and “180°” is notnecessary, and these terms represent the general direction of therespective components only.

In such a case, said second product supply apparatus may include thesame pipeline production facility operable to supply continuous productonto a storage carousel via substantially the same curved path in afirst phase of operation and then in a second phase of operation tounload the stored product via said 180° curved path substantially inreverse and thus into said second path and thence to the tower diverter.

Said 180° curved path may be defined by a diverter structure partiallysurrounding said carousel.

Said first product supply apparatus may include a horizontal pipestorage carousel for storing a length of pre-fabricated continuousproduct, the carousel being operable to unload said product into saidfirst path and thence to the tower diverter.

The same carousel may be operable as part of said first product supplyapparatus and as part of said second product supply apparatus, accordingto its direction of rotation during unloading.

The same carousel may be arranged to be loadable from an on-boardpipeline production facility and alternatively from an off-board supply(e.g. reeling on at port or possibly at sea), the direction of rotationduring unloading being different according to the source of supply.

A loading stinger may be provided on the vessel for receiving pipe fromsaid off-board supply.

The carousel may be substantially surrounded by a large radius diverterstructure, the product being diverted from storage on the carouselaround the outside of this structure whether serving as part of thefirst or second production apparatus. This structure, which may be acurved wall according to the first aspect of the invention above, mayserve for example to align the product with the direct production lines,and also to accommodate variations in winding height without requiringelevating support for pipe conditioning apparatus on said first andsecond paths. Elevating parts are not excluded by the invention,however.

The pipe launching apparatus may further include first and secondvertical radius controllers mounted at deck level for receiving theproduct and diverting the product upward from said first path and saidsecond path respectively toward said tower diverter means.

The first and second vertical radius controllers may include commoncomponents, these being transferable from the one side of the vessel tothe other side of the vessel according to which production apparatus isbeing used.

The first and second vertical radius controllers may be mounted forfore-and-aft movement to adjust their position according to theinclination of the tower structure.

The pipe launching apparatus may further comprise a straightenerassociated with each vertical radius controller for removing a plasticbending introduced by the vertical radius controllers. The straightenermay be mounted on a pivoting arm adjustable according to the inclinationof the tower structure.

Said tower diverter means may comprise a radius controller mounted onthe tower above said elevated position and movable between port andstarboard operating positions for receiving said product at a sideelevated position above whichever of said first path or said second pathis appropriate.

The radius controller may be movable between said port and starboardpositions by swinging it in an arc about a lay axis of the pipe handlingmeans. The tower diverter means may further comprise a straightenersupported so as to move together with the radius controller.

The radius controller may further be operable at a central position forreceiving elongate article from a central product supply apparatus atdeck level. This may be for example a supply of flexible pipe.

In a second aspect, the invention provides an apparatus for layingcontinuous rigid pipe from the deck of a vessel at sea, the apparatuscomprising

-   -   pipe supply apparatus arranged on said deck;    -   pipe launching apparatus for receiving the pipe from said supply        apparatus and for launching the pipe into the sea at an angle        greater than 60° to the horizontal;        wherein the pipe supply and launching apparatus together define        a path for the pipe such that the pipe is subject to plastic        bending sequentially in first and second planes prior to launch,        the first and second planes being substantially perpendicular to        one another relative to the orientation of the pipe at        initiation of each bending.

By this means, the effects of bending, be they beneficial or detrimentaleffects, can be distributed evenly around the circumference of the pipe,rather than concentrated at certain “clock positions” and not others.Ovalisation of the pipe is also minimised by this arrangement.

The invention similarly provides a method of laying rigid pipelinewherein the pipe is subjected to plastic bending sequentially in firstand second planes prior to launch, the first and second planes beingsubstantially perpendicular to one another relative to the orientationof the pipe at initiation of each bending.

It is preferred to avoid twisting of the pipe, in which case the firstand second planes will be perpendicular in space. However, if the pipeis twisted between the two bendings, this will not necessarily be thecase, as the term “perpendicular” is with reference to the orientationof the pipe, rather than any absolute reference.

Where the pipe supply apparatus is arranged to release pipe in ahorizontal direction, the first plane of bending may be a substantiallyhorizontal plane and the second plane a substantially vertical plane.

Alternatively, the first bend may be in a substantially vertical firstplane and the second plane may be substantially perpendicular to thefirst plane and inclined at an angle similar to the pipe launch angle.

A first straightener may be provided for removing the bending in thefirst plane. The first straightener may be arranged to act prior tobending in the second plane. Alternatively, bending in both planes maybe followed by straightening in both planes.

In a preferred embodiment, said pipe launching apparatus includes:

-   -   an elevated structure for supporting the pipe at said launch        angle above deck level;    -   upward diverting means for receiving continuous pipe from said        pipe supply apparatus and imparting plastic bending to the pipe        in said substantially vertical plane to direct said pipe to an        upper part of said elevated structure;    -   an upper radius controller on the upper part of said elevated        structure for receiving the pipe from the upward diverting means        and diverting the pipe downward, substantially to said launch        angle;    -   a straightener for receiving the downward directed pipe from the        upper radius controller and removing at least the vertical        component of said plastic bending prior to launch of said pipe        into the sea.

The upper radius controller may be oriented so as to impart plasticbending in a plane substantially perpendicular to said vertical plane,or alternatively substantially in said vertical plane.

In the latter case, the form of the supply apparatus may be such as toimpart to the pipe plastic bending in a substantially horizontal plane,prior to said upward diverting means.

The supply apparatus may include a pipe storage reel mounted on thevessel. The bending in the first plane may be part of the reelingprocess, or bending in said first and second planes may be performed,subsequent to unreeling.

The supply apparatus may include a welding production line for producingsaid pipe from pipe sections on board the vessel for supply to said pipestorage reel. The first bending can be imparted during reeling.

The reel may be mounted horizontally, that is, with a vertical axis.Horizontal reels help in lowering the centre of gravity of thearrangement when laden with pipe, increasing the safe load for a givenhull.

The supply apparatus may be arranged to direct the pipe along a sidedeck of the vessel, the pipe being bent upward from said side deck thenbent toward the centre line of the vessel at an elevated location toreach the launch angle.

In such a case, the upper radius controller will be orientedtransversely to the centreline of the vessel. In accordance with anotheraspect of the invention set forth below, the upper radius controller maybe operable alternatively at port and starboard sides, to suit differentmodes of production.

In a different embodiment, the invention of the second aspect providespipe launching apparatus be arranged to direct the pipe from a supply atdeck level from one side of the vessel toward the vessel centreline andthen with bending in a horizontal plane substantially parallel to thecentreline of the vessel at deck level, the pipe then being bent upwardin a vertical plane to an elevated location and then downward in thesame vertical plane to reach the launch angle.

This arrangement permits a horizontal reel to be combined with a centraltower or stern ramp. The supply of pipe from a horizontal reel comesnaturally from one side of the reel, even though the reel is generallymounted on or very close to the vessel centreline.

Where means are provided for performing said bending in the horizontalplane on pipe received directly from the reel, said means may be mountedon an elevating support to track the varying height of product windingson the reel. In one particular embodiment, pipe conditioning means foreffecting horizontal bending and straightening and also said upwardbending are mounted on a common elevating platform.

The supply apparatus may include a welding production line for producingsaid pipe from pipe sections on board the vessel for supply directly tosaid pipe launching apparatus.

The pipe launching apparatus may comprise a tower according to variousfurther aspects of the invention as set forth below.

The invention in a third aspect provides apparatus for diverting acontinuous pipeline for example during pipeline fabrication and/orlaying operations, the apparatus comprising effectively a wall curved inone dimension and extended in another dimension, whereby pipeline can bedrawn under tension around the wall so as to follow any one of manysimilar curved paths without moving the wall.

The wall may extend vertically, while curving horizontally, such thatsaid pipeline can be drawn different paths having substantially the samecurve horizontally but different elevations.

The wall may be formed by a plurality of parallel rollers arrayed alonga curved path, to reduce friction. Alternatively the wall can be asimple smooth surface, for example of steel.

The apparatus may comprise at least one auxiliary guide means (typicallya roller) movable in said other dimension parallel to the wall forconstraining the pipeline to follow the desired one of said curved paths(rather than relying on tension alone). This is particularly a concernwhere the wall extends vertically, as the weight of the pipe mayotherwise cause it to deviate from the desired path, and possibly causedamage.

There may for example be auxiliary guide means at one end of the wall toconstrain the point of entry or exit of the pipeline to or from thewall.

There may be a plurality of adjustable guide means spaced around thewall and movable so as to constrain the pipeline at a number of pointsalong the curved path. The plurality of guide means may be adjustableindependently of one another, so that the position of said pipe can varyin said other dimension as the path progresses around the wall.

The apparatus may be arranged to feed said pipeline to or from a pipestorage reel, the selected path varying as winding/unwinding progressesin the axial direction of the reel.

The apparatus may in particular be arranged for interfacing between thereel, where pipe exits or enters the reel at varying axial positions aswinding progresses, and pipe conditioning apparatus substantially fixedin the direction of the reel axis. Thus the conventional “level winder”mechanism is avoided or simplified. It may still be desirable for thepipe conditioning apparatus (for example a straightener) to beadjustable in orientation, to account or slightly different angles ofpipe path.

All or part of the wall may be mounted so as to be movable to vary theselection of curved paths in a further dimension.

In a preferred embodiment, the curved wall of the pipeline divertingapparatus comprises a fixed curved wall portion and a movable curvedwall portion pivoted about an axis adjacent an end of the fixed wallportion so as to vary curved paths available from the fixed wallportion. The movable wall portion may have a radius of curvature smallerthan the fixed portion, the pivot axis of the movable portion being setback within the radius of the fixed wall portion. Guide means movableparallel to the reel axis may be provided at or near the extremity ofthe movable wall portion closest to the reel, so as to constrain thepipeline to an appropriate axial position for orderly winding.

Where the apparatus is arranged to feed said pipeline to or from a pipestorage reel, the part of the wall closest to the reel may be arrangedto move radially relative to the reel as winding/unwinding progresses inthe axial direction of the reel. The wall may for example be mounted topivot about an axis parallel to the axis of the reel.

The wall may be arranged so as to be curved around the location of apipe storage reel. This space-saving arrangement is possible, whetherthe wall is to function in association with the reel or is for unrelatedoperations.

The invention in this third aspect further provides a reeled pipestorage apparatus comprising a pipe storage reel and the divertingapparatus as set forth above, the curved wall of the diverting apparatuspartially surrounding the reel.

The diverting apparatus may be arranged for receiving pipeline from thesupply and guiding it to the reel during winding. The divertingapparatus may be arranged for receiving pipeline along either of twoalternative paths during reeling, including a first reeling path runningclockwise around the curved wall and onto the reel and a second reelingpath running anticlockwise around the curved wall and onto the reel.

The diverting apparatus may be arranged for receiving pipeline from thereel during unwinding thereof and guiding it to pipe launchingapparatus. The diverting apparatus may be arranged for guiding thepipeline along either of two alternative paths during laying, a firstunreeling path running anticlockwise around the reel and onto the curvedwall and a second unreeling path running clockwise around the reel andonto the curved wall.

The optional features of the diverting apparatus mentioned above applyequally in this context.

In a preferred embodiment, the curved wall of the pipeline divertingapparatus comprises a fixed curved wall portion and two movable curvedwall portions, pivoted about respective axes adjacent opposite ends ofthe fixed wall portion so as to offer a bridge between the variableradius of windings on the reel and the fixed radius of the fixed wallportion, whether the reel is wound clockwise or anticlockwise.

Each movable wall portion may have a radius of curvature smaller thanthe fixed portion, the pivot axis of the movable portion being set backwithin the radius of the fixed wall portion.

The fixed wall portion may have a radius of curvature in excess of 15 mor 20 m.

The invention in a fourth aspect further provides a reeled pipe storageapparatus comprising a pipe storage reel having a vertical axis and atleast one spooling arm comprising a movable curved wall, the movablecurved wall being fixed vertically and extending over substantially theloadable height of the reel for supporting and diverting the pipe undertension between the reel and pipe handling apparatus, and being movable(for example pivotable about an axis parallel to the axis of the reel)such that one end of said wall is movable within the reel toward andaway from the reel axis, according to the radius of wound pipe, whilethe other end maintains a substantially constant position for conveyingthe pipe to or from other apparatus.

Guide means (typically rollers) movable parallel to the reel axis may beprovided at or near the extremity of the movable wall portion closest tothe reel, so as to constrain the pipeline to an appropriate axialposition for orderly winding.

In a preferred embodiment, first and second spooling arms are providedfor guiding pipe along either of two alternative paths during reeling,the first spooling arm defining part of a first pipeline path runningclockwise onto the reel and the second spooling arm defining part of asecond pipeline path running anticlockwise onto the reel.

The fixed wall portion may have a radius of curvature in excess of 15 mor 20 m. It may have a height in excess of 5 m. These values allow avery large capacity reel, and also minimise damage to the pipe.

The invention further provides methods of fabricating, reeling, layingand otherwise processing pipe as suggested by the apparatus of thefirst, second and third aspects of the invention set forth above, and asexemplified in the detailed description of embodiments further below.

In a fifth aspect, the invention provides a pipe laying vessel having acarousel arrangement providing separate first and second storage meansfor respective stocks of continuous elongate articles (for exampleso-called rigid pipe, but also flexible pipes, cables, chains, rope orwhatever) wherein the first and second horizontal pipe storage carouselsare arranged on substantially a common vertical axis.

The carousel arrangement may provide means for driving each of saidstorage means to rotate around said axis for loading or unloading therespective article. The driving means may be adapted for driving bothstorage means at independently controlled rates of rotation.

The driving means and other apparatus on the vessel may be operable suchthat one of said storage means can be unloaded for launching itsrespective elongate article into the sea, while the other of the storagemeans is rotated to load it with new stock of elongate article.

The vessel may be further provided with pipeline fabrication means forfabricating continuous rigid pipeline from a store of pipe sections. Theloading may alternatively be from auxiliary storage reels, for examplein the case of flexible pipe, rope etc.

The second storage means may be positioned above the first storagemeans.

The second storage means may be nested at least partially within thefirst storage means.

The first storage means may comprise a reel, the reel having a hubsurrounding the axis and being adapted for winding the respectiveelongate article onto the outside of said hub. The hub may be a rightcircular cylinder, or frusto-conical, for example.

In a first preferred embodiment, the first storage means comprises areel having a hub surrounding the axis and being adapted for winding therespective elongate article onto the outside of said hub, while thesecond storage means comprises a containment for located in a spacewithin the hub of the reel, the second storage means comprising acylindrical containment wall and floor adapted to contain a coil forstoring a flexible elongate article and means for loading and unloadingthe article from above.

The carousel arrangement of the fifth aspect of the invention maynaturally be combined with the inventions of the first, second, thirdand fourth aspects, and further aspects below, or may be usedindependently.

The invention further provides methods of fabricating, reeling, layingand otherwise processing pipe as suggested by the apparatus of the fifthaspect of the invention set forth above, and as exemplified in thedetailed description of embodiments further below.

The invention in a sixth aspect provides a sea-going vessel having pipelaunching apparatus which comprises:

-   -   pipe section supply apparatus for supplying lengths of pipe from        a store on board the vessel;    -   a first tower section mounted on the vessel and inclinable to a        desired launch angle to align with a catenary curve of a        continuous pipe suspended below the vessel;    -   pipe handling means mounted on the first tower section for        receiving pipe from said supply apparatus and for gripping and        supporting the weight of the suspended pipe while paying it out;    -   an upper work station mounted at the top of the first tower        section for joining a new length of pipe supported above said        work station to the suspended pipe; and    -   a second tower section operable in an extended position above        the first tower section for receiving said new length of pipe        from said pipe section supply apparatus and supporting it during        said joining at the first workstation,        wherein said pipe section supply apparatus, upper work station        and handling means are operable in cycles to add successive        lengths of pipe to the suspended pipe, and wherein said second        tower section is collapsible telescopically into a collapsed        position within the first tower section when not in use.

There may further be provided a lower workstation near the bottom of thefirst tower section. Depending on the height of each tower section, suchan arrangement enables rapid laying of double joints or preferably quadjoints. By providing a work station elevated at the top of the firsttower section, and also one at the foot of the first tower section (neardeck level), two joints can be worked on in parallel. At the same time,the upper section can be relatively lightweight, and can be lowered toimprove the stability of the vessel in poor weather, and in transit. Theexpression “within the first tower” is not intended to limit theinvention to cases where the first tower section actually surrounds thesecond tower section to any set degree. The two structures may inpractice rest alongside one another.

The pipe handling means may comprise at least one travelling clampmounted to travel up and down the first tower section on a carriage tocontrol paying out of the pipeline.

The carriage may be operable to elevate and lower the second towersection, while separate fixing means are provided for retaining thesecond tower section in said extended position.

There may be further provided an alternative supply apparatus forcontinuous elongate product, including means at an elevated position onthe first tower section for receiving said continuous product from decklevel, the pipe handling means mounted on the first tower section beingadaptable for continuous paying out of said continuous elongate product.

The ability to use the same handling means for continuous and step-wiseproduct adds considerably to the compactness, cheapness and versatilityof the vessel.

In a preferred embodiment where said pipe handling means comprises afirst travelling clamp mounted on a carriage as mentioned already, saidhandling means may further comprise a second travelling clamp mounted ona second carriage movable up and down within at least a lower part ofthe first tower section, the first and second travelling clamps beingoperable in a hand-to-hand sequence with both clamps moving reciprocallyand alternately gripping the continuous elongate product to effectcontinuous paying out of said continuous elongate product.

The or each travelling clamp may comprise plurality of individual ramunits arrayed around and along a length of the product path. Drive meansmay be provided in the form of an incompressible segmented rack. Thesefeatures are the subject of earlier patent applications by the presentapplicant, for example GB 2 364 758 A and GB 2 370 335 A (agents' ref63566GB and 63591GB), the contents of which are incorporated herein byreference.

The second travelling clamp need not travel up and down the first towersection during operation of the pipe section supply apparatus, wherepaying out is naturally step-wise and the ability to move the productcontinuously is not an advantage. For reeled pipe, however, the abilityto lay at a continuous rate is very important because of the enormousinertia of the laden reel.

In the embodiments to be described, the travelling clamp carriage(s) is(are) trapped at the lower part of the first tower section while thesecond tower section is collapsed into the first tower section, but thislimits operational flexibility and need not be the case. The secondtower section may in any case be made demountable, leaving only oneworkstation at deck level. If the first tower section is quad jointlength, then quad joints can still be laid, but at a reduced ratebecause all work steps must be carried out at the same work station.

Where a lower work station is provided near the bottom of the firsttower section, it may be mountable on the carriage of the secondtravelling clamp. In this way, although the second carriage is normallyfixed in J-Lay operations, the workstation can be moved to a differentheight to accommodate non-standard operations. Each of the clamps andthe workstation may be retractable into the tower to allow passage ofbulky accessories such as pipeline end terminations (PLETs), anodes andthe like.

The lower workstation may be mounted on a platform inclinable relativeto the second carriage, so as to maintain it horizontal at differentlaunch angles.

As an alternative to travelling clamps, of course track-type tensionersor other handling means can be employed. Track tensioners for supportingvery heavy loads tend to be very heavy compared with equivalent clamps,however.

The invention in a seventh aspect provides a sea-going vessel havingpipe launching apparatus for launching an elongate product, the pipelaunching apparatus comprising:

-   -   a tower structure;    -   product handling means within said tower structure operable to        receive said product at an elevated position and to align it        with said launch angle and for gripping and supporting the        weight of the suspended product while operations are performed        upon it; and    -   a workstation comprising a platform for supporting machinery and        personnel appropriate to said operations,        wherein the pipe handling means includes at least one travelling        clamp mounted to travel up and down at least a part of the tower        structure on a carriage, and wherein said work station is        mountable on the carriage of the travelling clamp to travel with        the clamp.

In this way, although the second carriage is normally fixed in J-Layoperations, the workstation can be moved to a different height toaccommodate non-standard operations.

The tower structure may be inclinable to a desired launch angle to alignwith a catenary curve of said product suspended below the vessel, themounting of the platform on the carriage being adjustable to maintainthe workstation in a horizontal attitude at a range of different launchangles.

The workstation may be retractable from the line of the product whileremaining on the carriage. The clamp may be retractable from the line ofthe product independently of the work station.

The travelling clamp may be one of two travelling clamps mounted onindependent carriages.

The invention in a eighth aspect provides a sea-going vessel having pipelaunching apparatus which comprises:

-   -   a tower structure mounted on the vessel and inclinable about a        horizontal tower pivot axis to a desired launch angle to align        with a catenary curve of a continuous elongate product suspended        below the vessel; and    -   pipe handling means mounted on the tower structure for receiving        pipe from a supply apparatus and for gripping and supporting the        weight of the suspended pipe while paying it out at said launch        angle,        wherein said tower structure is mounted above a moonpool of the        vessel and said tower pivot axis is substantially below main        deck level, for example 2 m, 2.5 m, 3 m or more.

It is advantageous to have the pivot point close to the neutral point ofthe vessel, while conventional tower designs do not achieve this. Theclaimed arrangement affords a lower centre of gravity and a better rangeof launch angle for a given size of moonpool. It will be understood bythe skilled person that the main deck of a vessel is readily identified,even though higher decks (shelter decks, working platforms etc.) may bepresent in known vessels, which may be higher than the tower pivot axis.

The invention in an ninth aspect provides a sea-going vessel having pipelaunching apparatus which comprises:

-   -   a tower structure mounted on the vessel and inclinable about a        horizontal tower pivot axis to a desired launch angle to align        with a catenary curve of a continuous elongate product suspended        below the vessel;    -   pipe handling means mounted on the tower structure for receiving        pipe from a supply apparatus and for gripping and supporting the        weight of the suspended pipe while paying it out at said launch        angle; and    -   at least one extendable strut supporting said tower structure at        a point above said pivot axis to control the inclination of the        tower structure,        wherein said extendable strut extends between said point on the        tower structure and a fixed point on the vessel, said fixed        point being provided by a raised structure substantially above        main deck height.

The extendable strut may comprise an hydraulic ram operable to elevatethe tower through its full range of inclination in a single stroke.

Auxiliary locking means may be provided to secure the tower at thedesired angle in case of power failure.

The invention in a tenth aspect provides a sea-going vessel having pipelaunching apparatus for laying continuous elongate product, the pipelaunching apparatus comprising:

-   -   product supply apparatus arranged substantially at deck level;    -   a tower structure including pipe handling means for receiving        said product at an elevated position on a launch axis and        supporting the weight of the suspended product while paying it        out along the launch axis; and    -   tower diverter means including a radius controller mounted on        the tower above said elevated position for receiving said        product from deck level at another elevated position away from        the launch axis and for supporting the product in a curved path        to said elevated position and aligning it with said launch axis        angle; and    -   auxiliary diverter means in the form of an A-frame having legs        arranged to pivot on either side of the radius controller and        tackle for supporting a load between distal ends of the legs so        as to describe an arc in the plane of said curved path but at a        greater radius.

The auxiliary diverter can be used for passing non-uniform portions ofthe product over the radius controller, where they would otherwise causedamage to the product and/or the apparatus.

The pivoting of the A-frame may be controlled in operation by one ormore extendable struts such as hydraulic rams.

The tackle on the A-frame may include a winch.

The A-frame need not have any particular shape. A rectangular form inwhich the legs are parallel and bridged by a boom provides goodclearance for the accessories being handled.

The radius controller and auxiliary diverter may be movable between saidport and starboard positions by swinging it in an arc about a lay axisof the pipe handling means. The tower diverter means may furthercomprise a straightener supported so as to move together with the radiuscontroller.

The radius controller may further be operable at a central position forreceiving elongate article from a central product supply apparatus atdeck level. This may be for example a supply of flexible pipe.

The invention in a eleventh aspect provides a method of deploying orrecovering an article from the seabed using a sea-going vessel havingpipe launching apparatus for launching elongate products, the pipelaunching apparatus comprising a tower structure including producthandling means operable to receive said product at an elevated positionand to align it with said launch angle and for gripping and supportingthe weight of the suspended product while operations are performed uponit, the pipe handling means comprising at least one travelling clampmounted to travel up and down at least a part of the tower structure ona carriage, the method comprising attaching the load to an elongatearticle of a type grippable by said travelling clamp and using thetravelling clamp to hoist or lower the load.

In a preferred embodiment, where said pipe handling means comprises afirst travelling clamp mounted on a carriage as mentioned already and asecond travelling clamp mounted on a second carriage movable up and downwithin at least a lower part of the first tower section, the methodcomprises operating the first and second travelling clamps in ahand-to-hand sequence with both clamps moving reciprocally andalternately gripping the elongate article to achieve continuous hoistingor lowering.

The elongate article used to support the load may be a flexible pipe,drill pipe sections, wire rope, or even chain. The clamps may be fittedwith adaptor shoes as appropriate.

The load being abandoned or recovered may be pipeline or other elongateproduct previously paid out using the same pipe handling means.

The invention in this aspect avoids the need to provide a crane ofcapacity equal to that of the product handling clamps in order toperform abandonment and recovery (A&R) operations with the largestloads. A smaller capacity crane can be provided for routine A&Roperations which do not require the full capacity.

The invention in a twelfth aspect provides a method of adapting a vesselpreviously operated as a hydrocarbon production and storage vessel foroperation as a pipe fabricating and laying vessel, wherein at least onestorage tank is adapted for storing sections of pipe for pipelinefabrication.

The adaptation may be reversible, such that at least bottom and sidewalls of said tank remain intact after adaptation.

The invention in a thirteenth aspect provides a method of adapting avessel previously operated as a hydrocarbon production and storagevessel for operation as a pipe laying vessel, wherein a raised deck isconstructed to provide working space for said pipe laying operationwhile leaving substantial pipework associated with said production andstorage operations intact beneath the raised deck.

Both of the twelfth and thirteenth aspects have the advantage that theconversion for pipelay operation is relatively cheap and reversible, andthe capital risk of the project is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, by reference to the accompanying drawings, in which:

FIG. 1 is a side view of a known laying vessel (Seaway Falcon), showinga deck-mounted firing line deploying via a stem-mounted vertical layramp;

FIGS. 2 a and 2 b are a side and plan view respectively of a known reellaying vessel (Apache), showing a deck-mounted vertical reel deployingvia a stem-mounted vertical lay ramp;

FIGS. 3 a and 3 b are side elevation (part cut-away) and plan viewrespectively of a novel pipelaying vessel, having a “horizontal”(vertical-axis) reel and an aft-leaning tower;

FIG. 4 a is a more detailed plan view of a product carousel andloading/unloading apparatus of the vessel of FIGS. 3 a and 3 b,

FIG. 4 b is respectively a cross-sectional elevation of the productcarousel FIG. 4 a of said vessel, and

FIG. 4 c is a side elevation of the carousel, with spooling arms;

FIGS. 5 a and 5 b are more detailed views of the tower of said vessellooking from port and from forward, respectively, and

FIG. 5 c is a view looking port of the tower and the angle through whichit operates;

FIGS. 6 a to 6 c comprise more detailed isometric plan andcross-sectional views of a pipe handling clamp arrangement used in thetower of said vessel;

FIG. 7 is a more detailed plan view of a departure roller arrangementmounted at the base of the tower of said vessel, showing both engagedand disengaged configurations;

FIGS. 8 a and 8 b are a detailed side elevation and plan viewrespectively of an A-frame arrangement on the tower radius controller,for passing large bodies over the radius controller and for Abandonment& Recovery (A&R) operations;

FIGS. 8 c and 8 d are a side and plan view respectively of the towerclamp drive system and radius controller;

FIGS. 9 a and 9 b are side and plan views of the tower pipe elevatorsystem in use at different stages of J-Lay operation;

FIG. 9 c is a more detailed view of the bottom of the tower and awelding station within the tower, with the tower inclined;

FIG. 10 is an isometric view of the pipe train of said vessel,configured for the direct deployment of on-board welded product via amoonpool, including two alternative welding lines;

FIG. 11 is an isometric view of the pipe train of said vessel,configured for the deployment of on board welded rigid product from thecarousel via the moonpool;

FIG. 12 is an isometric view of the pipe train of said vessel,configured for the carousel reeling or deployment of pre-welded rigidproduct via a side-mounted stinger;

FIG. 13 is an isometric view of the pipe train of said vessel,configured for the deployment of stinger-loaded rigid product from thecarousel via the moonpool;

FIG. 14 is an isometric view of the pipe train of said vessel,configured for the carousel reeling of on-board welded productsincluding two alternative welding lines;

FIG. 15 is an isometric view of the pipe train of said vessel,configured for the loading/deployment of flexible product to/from acentral carousel basket via a side-mounted stinger;

FIG. 16 is an isometric view of the pipe train of said vessel,configured for the deployment of flexible product from a centralcarousel basket via the moonpool;

FIG. 17 is a side view of a vertical radius controller and secondstraighter of said vessel;

FIG. 18 a and 18 b are a side and plan view respectively of anAbandonment and Recovery (A&R) system of said vessel, configured fordeep A&R;

FIG. 18 c is a side view of the Abandonment and Recovery (A&R) systemconfigured for shallow A&R;

FIGS. 19 a and 19 b are a side (part cut-away) and plan viewrespectively of second novel pipelaying vessel, having a stem-locatedmultiple spool carousel, a mid-line pipe train and a forward-leaningtower;

FIGS. 20 a and 20 b are more detailed side and plan views of theelevating platform of the vessel of FIGS. 19 a and 19 b; and

FIGS. 21 a and 21 b are a side (part cut-away) and plan viewrespectively of a third novel pipelaying vessel having a forward-mountedcarousel, a mid-line pipe train and a stem lay ramp; and

FIGS. 22 a and 22 b are more detailed side and plan views of theelevating platform of the vessel of FIGS. 19 a and 19 b.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 shows schematically the arrangement of a known pipe laying vessel10, known commercially as “Seaway Falcon”, having a deck 12, on which ismounted a pipe line assembly arrangement 14, comprising various welding,coating and testing stations for assembling a continuous pipeline from astock of pipe segments. Pipe 16 formed in this way progresses in thedirection of the arrow, over first and second radius controllers 18, 20.A tiltable ramp 22 is provided for launching the pipe over the stern ofvessel 10. In solid lines, ramp 22 and other equipment are shown in anear-horizontal orientation, appropriate to lower water depths. Inchain-dotted lines, the same components are shown in a steeply elevatedorientation, with the reference signs primed (22′ etc.). The radiuscontrollers 18 to 20 guide the pipe and restrict within set limits,according to the angle of the ramp 22. On ramp 22 there are mountedvarious pipe handling devices, namely: straightener 24, tensioning andpaying-out device 26 and fixed clamp 28.

Seaway Falcon does not provide support for reel lay, and is thereforeincapable of laying long continuous lengths of rigid product. The vesselis, furthermore, restricted in size and as a result not ideally suitedfor deep lay operation.

FIGS. 2 a and 2 b are side and plan views respectively of a known reellaying vessel/barge 40 as disclosed in U.S. Pat. No. 4,917,540, andknown commercially as “Apache”. The vessel has forward 42, midship 44and stern 46 sections, and a reel 50 mounted at the midship sectionhaving a horizontal axis of rotation extending transversely of the ship,such that the load of the reel is distributed downwardly and outwardlysubstantially in the direction of the longitudinal axis of the ship. Theship further includes pipe conditioning apparatus 54 located at thestern section and a radius controller 56 after it is unspooled from thereel, both of which are mounted upon a lay tower 52. A straightener 58imparts a reverse bending force to the pipe opposite to the curvatureimparted to the pipe by the reel. The pipe entry angle at which pipeenters the sea is altered by varying the angle of the lay tower, asindicated by the hashed outline of the tower. The vessel is not easilyconverted for deployment of articles having different mechanicalproperties, such as flexible conduit, or power cable. Furthermore, thestages that involve bending of the pipe; that is loading to the reel,and unloading from the reel, and for guiding the pipeline through theguiding mechanism into the sea, all occur in substantially the same,horizontal plane. As a result, the size and weight of the reel islimited to the height of the centre of gravity of the vessel that can betolerated without creating unacceptably high risk of instability,thereby limiting the lay length achievable with such a configuration.

A new design of pipelaying vessel is hereby presented (and variants),which overcomes many of the disadvantages and limitations of theaforementioned vessels.

Offshore construction systems are designed and specified to undertakedeployment (and recovery) operations for projects expected in theforeseeable future. The systems are particularly targeted towards thedeepest developments planned anywhere around the world, although pipedeployment in 150 m water depths (or less for smaller pipes) is equallydesirable. One of the goals of the new vessel design is to provideincreased payload capacity, allowing projects to be undertaken with theminimum number of intermediate mobilisations. The ship size and draftcan inhibit the ability to visit certain ports and product manufacturingfacilities. This has also been accommodated in the design.

The key requirements for the new vessel are to provide as a minimum thefollowing in-field facilities:

-   -   On-board manufacturing of rigid pipe using a conventional firing        line and/or a Radial Friction Welding process.    -   Deployment of rigid pipe up to quad-joint length by J-lay.    -   Deployment of rigid pipe by continuous lay from a Carousel.    -   Deployment of flexible pipe from a Carousel or standard reels.    -   Deployment of umbilicals.    -   Attachment and subsequent deployment of Pipeline Structures        (PLET's, etc).    -   Deployment of 600te seabed structures by heave compensated        lowering.    -   Top tension capability of 1500 tonnes    -   Extensive pipe joint storage

The design goal is to satisfy all of these requirements by designsinvolving many novel features.

The vessel's capabilities are summarised in the following table:

Product Operation Product Source Rigid Pipe J-lay of quad-jointson-board Firing Line J-lay of continuous pipe on-board Firing LineContinuous lay Carousel Flexible Pipe Carousel Basket or standard 9.2mreels Pipeline Structures Attachment to pipe and (PLET's, In-linedeployment ‘T’s, etc) Seabed Structures Deployment to the seabed

FIGS. 3 a and 3 b are side and plan view respectively of a first,preferred, embodiment of an improved pipelaying vessel 80, arranged toprovide the required capability. The vessel comprises a lower deck 100,which is part of the original superstructure, upon which is mounted anupper deck 102, providing support for the majority of the pipelayingapparatus.

Equipment Summary

The following equipment is provided upon the upper deck 102, asillustrated in the accompanying figures, provided with the references asshown and described in detail later.

System Components Lower Tower and tilt Lower Tower structure, tilt rams,support system structure Deployment Clamps with associated carriage anddrive systems Radius Controller Arch Straightener. Two enclosedworkstations in the Tower providing welding, NDE and coating facilitiesPipe-stock elevating system Upper Tower Upper Tower structure, and pipestock transfer apparatus Loading/Deployment Stinger structure andassociated equipment Stinger Tensioner Straightener Pull through 300teWinch Equipment Rope Storage Drums Diverter Sheaves A& R system Nospecific components Carousel Carousel Reel(s) and Basket Rigid ProductSpooling Arms Carousel Basket Basket Product Manipulators/Gantry PipeBending 23m Horizontal Radius Controller 12m Vertical Radius Controller3 x straighteners Pipeline Manufacture Port firing line - 6 stations(double joints) Tensioner Radial Friction RFW Machine and associatedequipment and Welding structures Standard Reels (project Dolly Basessupply) Tensioner Pipe Storage Racks Pipe Handling facilities in tanksPipeline Structures Handling Facilities Craneage 600 t overboardingcrane 2 × 70te knuckleboom deck cranes 1 × 30te stores crane (poop deck)ROV systems Raised Deck Ship interface

The vessel employs a forward-located configurable product carousel 104(comprising nested outer rigid product carousel 1040 and inner flexiblesbasket 1042), a rearward-leaning tower 106 (comprising a massive lowertower 1060, and a frame-like upper tower 1062) for deploying via amoonpool 108 and a side-mounted stinger 110 for loading and deployment.The centre of gravity of the carousel, and therefore the load, is low,while the capacity provided is high, with much less onerous effects onthe stability of the ship than a horizontal axis reel providing the samecapacity.

Elongate articles are laid from the vessel in a variety of ways, all ofwhich use common pipe apparatus, which includes product firing lines112, 114, 116, straighteners 118,119, 120, tensioners 122, 124, 125,126, reaction tracks 123, a forward-mounted radius wall 128, carouselreeling/unreeling arms 130, 134, one or more vertical radius controllers136, 138, a tower-mounted rotatable vertical radius controller 140.

Support equipment for the laying operations comprises Abandonment andRecovery equipment 142, 144, 146, 148, a pipe elevator system 150 fortranslating large-diameter rigid pipe lengths from the deck into thetower, various cranes 160, 162, winches and product storage facilities170.

Functional Overview

There follows a brief overview of the equipment. Further detailed isprovided in the corresponding sections later within this document.

Deployment

The Lower Tower 1060 and its associated equipment forms the fundamentaldeployment medium. Product is deployed by the movement of DeploymentClamps (210, 220 not shown) within the Tower. The clamps are capable ofmoving in a “hand-to-hand” mode providing a continuous speed ofdeployment. For J-Lay deployment, where rigid pipe is joined on board,the lower clamp remains static at the Lower Tower base while the upperclamp travels over the full track height.

The Upper Tower 1062 is capable of extending, to enable a greater speedof deployment of quad joints. This is due to the ability to performsimultaneous execution of welding and NDE/coating operations by beingable to hold quad joints in the Upper Tower.

Product up to ˜45 cm (18″) diameter can also be deployed or loaded usingthe stinger 110 configured to the side of the ship.

Pipe is joined either by a Radial Friction Welding (RFW) process 112 orin a Firing Line 114, 116, both located on the port side of the ship. Itcan then be deployed (or stored) by either:

-   -   as a continuous pipe routed around the 23 m radius wall 128 (aft        of Carousel 104), along the starboard side to a deck-mounted        vertical radius controller 136, over a Tower-mounted Arch 140        and to Deployment Clamps 219-220. Product is initiated and        terminated using a 300te winch, or    -   as a continuous pipe spooled onto a Carousel 104 for later        deployment, or    -   as pipe stocks transferred over pipe racks to a Pipe-stock        Elevator system. The pipe stock is raised to the top of the        Upper Tower 1062. From there it is transferred to the deployment        centreline where it is welded to the previous quad-joint length.        The Deployment Clamps lower the new section (now forming the top        of the catenary) into the Lower Tower 1060. Welding, NDE and        coating are also carried out at a Tower work station (see later        for detail).

Due to the flexibility of the pipe laying system, the skilled personwill appreciate that each firing line could be located on separate sidesof the ship, both firing aft. A port-located firing line would use astarboard-located vertical radius controller 138, and astarboard-located firing line would use a port-located vertical radiuscontroller 136. The tower vertical radius controller 140 would belocated to accommodate being fed from either vertical radius controller136, 138, but would deploy down the same clamps 210, 220 and moonpool108.

Seabed structures, such as suction anchors, manifolds, etc., aredeployed to 200 m by an overboarding crane 162 where they aretransferred to the rigging from the Tower 106. The Deployment Clampdrive system provides heave compensation control which allows thestructures to be lowered safely to the seabed. The same drive system isadapted to lower the Upper Tower 1062 for transit and raise it again foroperation.

Abandonment & Recovery (A&R)

Apart from specific A&R Rope, Storage Drum and diverter sheaves (seelater for detail), the A&R system has no specific equipment associatedwith it. Abandonment and recovery operations are executed using theDeployment Clamps 210-220 in the Tower as the hold-back/driving device.It is anticipated that in shallow waters an Initiation Winch will havesufficient capacity to perform A&R without having to use the DeploymentClamps.

On-Board Storage

The layout indicates substantial pipe rack storage on deck (185 forexample). Alternatively this space can accommodate standard 9.2 m reelson dolly bases 170, project equipment and containers or structuresassociated with the pipeline. The location of a 600 tonne crane 162 isselected so that the reels and the structures can be handledappropriately upon the deck.

Areas 185 a shown hatched indicate areas where the deck can be opened topermit storage of rigid pipe sections, flexible product and/or tools andother associated components in the existing storage tanks. Suitableracking and the like can be installed within the tanks, which can beremoved if the vessel should be returned to its original function.

Pipeline structures are handled into the Lower Tower 1060, and afterfine adjustment, welding, etc., they are deployed on the pipe catenaryby the Deployment Clamps 210, 220 to the seabed.

Carousel Reel and Basket

Product of all product types up to ˜45 cm (18″) diameter can be loadedonto the carousel 104 using the stinger 110 mounted on the starboardside of the ship. A tensioner 124 is provided to generate the requiredback-tension in rigid pipe product to properly spool onto the Carousel.

Rigid product is paid off the Carousel using an Offspool Arm 134. Thisallows pipe from any wrap on the Carousel to be aligned with thestraightener (straightener 118 is transferred to the appropriate side ofthe vessel to accommodate the carousel wrap direction) and deck-mountedvertical radius controller 136. The deployment route is the same as forthe continuous lay process.

Umbilicals are placed into the carousel's inner basket 1042 using aManipulator Arm 180 mounted on a gantry over the basket. A tensioner 126pulls the product to the basket. Payout of the product from the basketis a reverse process. The product is routed directly to the RadiusControl Arch 140 at the top of the Tower 106. The product is initiatedand terminated using the combined action of an A-frame 190 mounted onthe arch and a deck crane 160. A&R of heavy loads is executed by theTower equipment.

Other Systems

Pipelay departure monitoring systems.

Seabed positioning equipment.

ROV's, and the like, are provided as usual.

The apparatus is now described in more detail, with reference to therelevant Figure(s).

Standard Firing Line

The onboard production of pipeline welds is undertaken by a firing line112 (as shown in FIG. 3 b) performing conventional welding or byutilising the known ‘Serimer Welding System’ (for example Satumax™orbital welders from Serimer DASA, France). Pipes are welded togetherand deployed from the vessel in several manners, such as “continuous laymode” 112 where the product is routed to the tower 106, or by joiningsections (not shown) to form double or quad-joints for deployment usingthe tower configured for J-Lay (using the upper tower 1062). Whicheveroption is selected there is provided a welding firing line 112 thatcontains all the equipment needed to handle, line up, weld, inspect andcoat each completed welded joint.

Pipe is supplied to the vessel in various lengths ranging from 12 to 18m as single joints and up to 28 m in double joints, and the weldingstations as described above are established in specific, configurablelocations dependent on the pipe lengths being utilised. Pipe handling isundertaken using dedicated deck mounted pipe handling equipment (forexample, crane 162). Once at the weld station the pipe ends are alignedusing pipe alignment machines and internal clamps are employed to holdthe pipe ends together during pipe welding. Conventional stick weldingcould be employed to complete the welds but the known Serimer orbitalwelding system is the preferred method of welding. Once welded the jointis subjected to NDE inspection before having a field joint coatingapplied. The application of the field joint coating tends to be thelimiting speed factor in producing completed joints due to the lengthyapplication and cure times involved. The number of work stationsavailable combined with the pipe specification determines the optimumnumber of stations that are allocated to each process, and isconfigurable between projects. The vessel facilitates six work stations112 to be located on the port side and allows the welding, NDE and fieldjoint coating to be completed prior to the product passing the radiuscontrol wall en route to the deployment tower 106 or for loading ontothe Carousel 104.

The J-lay arrangement is readily accommodated by reconfiguring theworkstations into a different arrangement (not shown) to allow thecompleted pipe joints to be transferred to the product loading elevatorsystem.

Radical Friction Firing Line

The known Radial Friction Welding (RFW) System, as disclosed in theapplicant's granted United Kingdom Patent GB2329603, is used to join twopipe lengths together using friction of rubbing surfaces to generate theheat required to form a homogeneous weld. The overall system developedattaches a single pipe length of 6″ to 12″ pipe, of any consideredmetallic pipeline material, to another pipe or pipestring. It alsomachines both the inside and the outside of the completed weld andundertakes a Non Destructive Examination of the weld using an ultrasonictechnique prior to completion of field joint coating and stressrelieving activities. The whole process is undertaken very rapidly in afully automatic mode, although it is not so adaptable as the standardfiring line to different types of product.

As described earlier, the standard and RFW firing lines are illustratedas being mounted one above the other, but could equally well be locatedon either sides of the vessel, due to the flexibility of the pipehandling system.

Carousel

FIGS. 4 a, 4 b and 4 c are a detailed plan, cross-sectional elevationand side elevation view respectively of the vessel's Carousel 104, whichis a large, horizontally mounted reel 1040 for the storage of continuouslengths of rigid and flexible pipe product 1044, and in which is mountedan independently driven basket 1042 for holding particularly flexibleproduct 10422 such as umbilicals, or rope.

The assembly comprises:

-   -   An independently rotating reel 1040 with a base 10404 having an        outer diameter of 39 m.    -   A 24 m diameter hub 10406.    -   Upper keeper beams 10408 attached to the top level of the hub        required for maintaining product spooling.    -   An independently driven product basket 1042 located within the        hub.    -   Two independent drive systems 10410, 10412 (not shown), each        comprising four 200 kW six pole vector electric motors and        gearboxes and braking systems, controlled to enable fine        adjustment of product tension and deployment speed.    -   Vertical bearings 10414 and horizontal bearings 10416.    -   Two unspooling arms 130, 134 to guide the product from a given        wrap on the carousel hub 10406 to a constant departure point        over a series of acceptable bending radii.

The storage weight capacity of the Carousel 104 is 10,000 tonne ofproduct. This may be apportioned between rigid pipe on the reel 1040 andumbilical spooled into the basket 1042.

The Carousel reel 1040 and basket 1042 are positioned around a centrecore (king pin) 10418 and are rotated for spooling on and reeling offproduct. Both the drum and the basket rotate independently.

Rigid and flexible pipes are wrapped onto the reel's hub 10406 in asimilar controlled manner to wire rope on a winch drum. A tensioner 122,124, is required to provide the necessary product back tension to enabletight spooling onto the Carousel reel.

Spooling Arms 130, 134 (regions “D” and “A” respectively on FIG. 4 a)are located in conjunction with a large radius controller wall (regions“B” and “C” on FIG. 4 a) 128, located 3 or 4 meters outside of theCarousel rim. Their function is to guide rigid pipe product onto or offthe Reel 1040 at the required turn or wrap, and align product to astraightener 118 or tensioner 122, 124 fixed in position. There are twoarms provided, one for each wrap direction. The curvature of the rigidpipe in the horizontal plane is maintained greater than that of the Reelhub 10406 and the curvature of the rigid pipe in the vertical planemaintains the product within its elastic strain limits, i.e. withoutimposing any plastic deformation upon the pipe. The radius controllerwall 128 and the spooling arms 130, 134 also provide restraint, andtherefore protection, in the event that tension is lost in the productpipe and the pipe springs upon the carousel. As a result flailing actionof the product pipe is prevented.

FIG. 4 c is a side elevation of the carousel 104, looking in thedirection towards the bow of the vessel, showing the carousel reel 1040,and two offspool/spooling arms 130, 134, which are used to load productto, or unload product from, the reel. A pivotable arm 130, 134 isprovided for each product wrap direction (clockwise, or anticlockwisewrap, as dictated by the configuration of the pipe bending andstraightening system).

The carousel 104 is mounted upon a central kingpin 10418, and verticalbearings 10410.

Each pivotable arm 130, 134 comprises a series of vertical-axis rollers10430, arranged on a chassis to form effectively a curved wall extendingfrom the reeled product to a pivot point 10432. The tip of each arm hasa tip roller 10434 and reel contact rollers 10436. The arm is sprung ordriven such that the contact roller contacts the spooled product. Thisensures that the gap between the reeled product 1044 and the tip rolleris as short as possible, minimising the risk of undesirable bending ofthe product as it is spooled or unspooled. The reel contact rollers10436 minimise the friction between the arm 130, 134 and the reeledproduct 1044, as it is rotated past the arm. In alternative embodiments,the rollers may not be needed, and a smooth steel surface could suffice.

The product is kept from falling by gravity by being maintained underconstant tension. The tension force is provided by the drive systems10410, 10412 of the carousel and the first tensioner 124, 125 throughwhich the product passes. It is possible that for larger diameterproduct tension alone may be insufficient to support the product as itpasses around the radius wall, in which case vertical support rollers10450 may be employed to provide additional support and guidance for theproduct between arm 130, 140 and the first tensioner 124, 125. Thevertical support rollers 10450 also help to reduce twisting on the pipe,as the pipe passes around the radius wall 128.

The unspooled product 1044′ passes forwards towards the bow of the shipand around the 23 m radius wall 128 (the ends of which are visible inthe diagram and identified as 128′ and 128″), reversing its direction oftravel substantially 180° and back towards the stern of the vessel (asindicated by 1044″).

The large volume enclosed by the hub 10406 of the carousel is utilisedas a product storage basket 1042 in which long lengths of Umbilicals andFlexibles and their associated termination assemblies are stored.Umbilicals and Flexibles are laid into the basket using a ProductManipulator 10420 which guides the product into its stored spiral wrapswithout infringing the Minimum Bend Radius (MBR) for each product.

Carousels have a successful track record in the offshore constructionindustry, however the size and storage capacity is greater than anyother currently in use.

Fine control and quick response to required speed and back tensionchanges in the carousel are possible by the use of 6 pole vector motorsand an accurate control system, using a consistently low friction factorbearing arrangement 10414, 10416 for the rotating Carousel reel andBasket. Large bearing packs are located between the king pin and theCarousel 104, and low friction bearings are selected to minimise thedeadweight drag.

The Off-Spooling Arms 130, 134 are to follow the product spooling levelon the Carousel and the pivot point of the arm moves in conjunction withthe product wrap level.

For the required storage capacity, structural and equipment weight andcentre of gravity height is minimised to minimise adverse effects onship stability.

A rigid foundation grillage (not shown) is provided to ensure uniformload distribution from the vertical bearings, upon which the grillagerides.

The Carousel reel 1040 is driven by four variable speed motors 10410through reduction gearboxes. The speed of rotation is determined by acontrol system referencing against pipe tension payout sensors.

The Basket 1042 is driven by four variable speed motors (not shown)through reduction gearboxes. The speed of rotation is determined by acontrol system.

Mechanical brakes are used to hold the Carousel reel and Basket inposition should the power be removed from the Drive Motors.

To achieve the accurate control required for the Carousel rotation thelatest technology in Vector and Servo Drive systems is used.

It is also possible, as an alternative, to deploy flexible product byspooling onto industry standard 9.2 m diameter reels 170 and deployingdirectly from these. This does, however, limit the length of continuousumbilical that can be deployed.

It is also possible, as an alternative, to continuous 2/3 bend J-Layusing the on-board Firing Line.

Pivoting Tower

FIGS. 5 a and 5 b are respective port-facing and forward-facing views ofthe vessel's tower 106.

The Tower Structure comprises lower section 1060 and upper section 1062,each rising to 73.5 m and 126.5 m above the main deck respectively.

Foundations 10610 are formed between the aft bulkhead and cofferdam ofthe construction moonpool 108. The Tower 106 is mounted on a pivot 10612supposedly by these foundations and is held in place by a tilt mechanism10614 which acts against a mount 10615, located on the tower. It will beseen that the tower pivot axis is substantially below main deck level.

FIG. 5 c is a side view looking port of the tower raising tilting system10614, allowing the tower to be tilted from 90 degrees (vertical) to 60degrees to allow the deployment of product in varying (shallower) waterdepths. The Tilt Mechanism incorporates hydraulic rams 10616 and lockingstruts 10618. The locking struts 10616 allow the Tower to be supportedwith the rams 10618 relieved of hydraulic pressure. The capabilityrequirement for the Tilt Mechanism 10614 is optimised by the use of adeck-mounted support structure 200 limiting the length, stroke and loadcapacity requirement of the hydraulic rams.

A Radius Controller Arch 140 is located at the top of the Lower Tower1060 (shown in further detail in FIG. 8 a). Its function is to route theproduct from the deck mounted equipment to the product centreline in theTower whilst maintaining a bend radius of 12 m. The arch is supported bya transverse box girder 1402, on which the Arch is able to rotate sothat product can be directed to the Tower from either side of the ship.Umbilicals are directed into the Tower with the Arch at a 90 degreeposition.

Tracks 10620 for the Deployment Clamp Carriages 10630, 10632 areintegrated into the Lower Tower 1060 column structures.

The overall dimensions of the Tower are governed by the following designgoals:

-   -   To accommodate a track length for the Deployment Clamp Carriage        to deploy 56 m long quad-joints using a single stroke of the        Deployment Clamps. Similarly, the Upper Tower 1062 accommodates        a quad-joint to be held over the product held in the Clamps.    -   To accommodate, within the box columns, the Deployment Clamp        drive motors 10640 at the base of the Lower Tower 1060 and        personnel access up the Tower.    -   To allow space for the Deployment Clamps 210, 220 and Carriages        10630, 10632 to travel between the box columns and to retract        the Clamps clear of the product deployment centreline.    -   To found the columns within the width of the moonpool where        maximum local strength can be developed in the ship steelwork.

The Tower is designed to accommodate loading of:

-   -   1500te top tension from the product catenary.    -   250te pipe initiation tension around the Radius Controller Arch.    -   600te package for deep sea lowering.    -   In association with deadloads, environmental loads and the        effects of ship motions.

The purpose is to allow deployment (and A&R) of:

-   -   Rigid and flexible products.    -   By J-Lay or Reel-Lay methods.    -   Attachment of pipeline structures (e.g. PLET's, in-line ‘T’s,        etc).    -   Deployment of 600te seabed structures using a heave compensated        lowering system.

The following equipment is accommodated by the Tower:

-   -   Deployment Clamps 210, 220 and associated drive system.    -   Product Departure systems 10670.    -   Product Straightener 10650.    -   Pipe-stock elevation and transfer (to product centreline)        systems 150.    -   Materials handling facilities.    -   Enclosed work stations 10680 and personnel access.

The structures used in the tower construction are either box-sectiongirders and columns 1060 or lattice frame 1062 using tubular sections,both of which are standard construction forms. High tensile steel plateis used for the box sections, and is material widely used for specialapplications in offshore structures. The weight and associated highcentre of gravity has a significant effect on the product storage weightcapacity due to vessel stability. The risk of capsize is reduced by theuse of the high tensile steel plate and box section construction for theLower Tower 1060, reducing the structural weight, while maintainingstructural integrity and stiffness. Stability is also improved by theuse of permanent ballast in the ship.

The loads applied from the Tower to the ship structure are substantial.The ship structure is strengthened local to the Tower foundation 10610to resist the high loading and to accommodate tilt of the Tower.Location of the Tower at the stem end of the moonpool allows the bestuse of the ship structure for support.

The load transfer system 10660 from the Deployment Clamps 210, 220 tothe Lower Tower 1060 is optimised to minimise the compression forces onthe tower, and as a result, minimise the thickness and strength ofmaterials required in the tower's construction. The use ofincompressible segmented racks for elevating the Deployment Clamps 210,220, avoids the weight of the suspended product being transferredthrough the tower itself. The arrangement of the carriages and clampswithin the structure of the tower ensures that the weight of thecarriages and clamps, and any catenary, are shared between both sides ofthe tower.

It is possible, as an alternative, to deploy rigid pipes using Steep ‘S’lay. The associated stinger may also be used to deploy flexibleflowlines and umbilicals. Steep ‘S’ has the advantage of lower weightand centre of gravity of the deployment equipment and structures (Towerversus Stinger). However with steep ‘S’, the skilled person willappreciate that other measures may need to be added to enable deep sealowering of seabed structures; increase the specification of the 600tecrane to include heave compensation and deep sea lowering capability oruse a smaller version of the Tower.

Moveable Clamps

FIGS. 6 a to 6 c are more detailed plan and isometric views of thetower's pipe handling clamp arrangement.

The clamps are the subject of earlier patent applications by the presentapplicant, for example GB 2 364 758 A and GB 2 370 335 A (agents' ref63566GB and 63591GB). A lower friction grip moving clamp 210, and anupper similar clamp 220, each rated to 1500 tonnes holding capacity, areprovided to grip the product and deploy it to/from the seabed. This isin either a continuous moving “hand to hand” mode of operation for reellay or in a “lower clamp fixed, upper clamp moving” mode of operationfor J-lay, as illustrated in FIG. 8 c and 8 d, described in detaillater. Each clamp is mounted on a carriage 10630, 10632 that isconnected to an electrically driven rack and pinion system 10640 locatedwithin each leg of the tower. The drive system is based uponincompressible segmented racks, which ensure that the weight of theclamps and catenary is presented to the base of the tower, rather thanhanging off the top of the tower, which would be the case for moretypical systems, such as a pulley or chain system. By exchanging padsizes within each clamp, pipes ranging from ˜10 cm to ˜45 cm (4″ to 18″NB) in spooled reel lay mode, or up to ˜90 cm (36″ NB) in J-lay mode,can be laid. The clamps are also able to grip J-lay collars, and can beconfigured to grip wire for Abandonment and Recovery operations. Forreel lay, both clamps 210, 220 move relative to each other, in asequential manner to and from the middle of the tower, to hand over thegrip on the product from one clamp to the other. The PLC controlledsequence will enable the minimum required continuous rate of deploymentor recovery of 12 metres per minute to be achieved. In this mode ofoperation to achieve the optimum lay rate with the smoothest continuousoperation neither clamp need travel more than half the distance of thetower. The PLC controlled sequence will ensure that while the product isbeing lowered by a gripping clamp, the other released clamp istravelling back to its starting point, where it is commanded to regripthe product, the tension being handed over from one clamp to another.

For J lay, the lower clamp remains at the base of the tower whilst theupper clamp travels the full length of the tower 1060 to hand over thegrip on the product in a stop-start manner. This PLC controlled methodof deployment enables quad joints of pipe to be laid at the minimumrequired rate of 3.5 km/day.

The moving clamp concept has been selected in preference to conventionaltensioners primarily due to required space and weight considerations.The moving clamps 210, 220 are controlled by the same PLC systems thatcontrol tensioners. The tensioner control systems are now wellestablished offshore, using the same technology for the moving clampsdoes not generate any technical problems. Of course, track typetensioners could be used within the tower as an alternative oradditional pipe handling means, if the application requires it.

Product Departure System

FIG. 7 shows a detailed plan view of the product departure roller box10670 at the base of the tower, with three sets of actuated rollers10672 operated by independent hydraulic rams 10674 that can extend andopen out into the moonpool area 108 to capture pipes ranging from ˜10 cmto ˜90 cm (4″ to 36″). Once captured and dependent on the outsidediameter of the pipe, the PLC controlled hydraulic cylinders areactrivated to pull the pipe into a central position below the clamps.For deployment of large articles, such as PLETs, the roller box isretracted and stowed between the tower columns to allow the articles topass.

Radius Controller A-Frame

FIGS. 8 a and 8 b show a detailed side elevation and plan viewrespectively of the tower radius controller 140, on which is mounted an“A-Frame” 190, capable of driven rotation about the same plane as theradius controller 140 by being mounted upon a pivot 1406.

The A-frame is driven at the pivot point by pinioned drive motors 1408.

To enable wire connections and any flexible end terminations to bepassed over the tower radius controller 140, the A-Frame 190 is providedwith a small winch 19010 mounted upon its cross member 19020 andconnected to the radius controller wheel structure.

In addition to Pipe Line End Terminations (PLETs), rigid products andflexibles may have a lay down head or other type of end termination. Forproduct deployment to the seabed, an A&R rope is connected to theproduct end termination at deck level. To assist in taking this endtermination around the tower radius controller arch 140, the A-frame 190with underslung winch 19010 at the top of the arch is used. Accesswalkways 1404 are provided at the top of the radius controller to allowthe wire from the A-frame winch to be connected to the product endtermination to lift it away from the arch. As the tower clamps 210, 220deploy the product down and through the moonpool, the radius controllerA-frame 190 will guide the end termination around the arch. Once aroundthe arch, the A-frame winch wire is disconnected and the tower clamps210, 220 are used to lower the product to the seabed using the A&R rope.

Pipe Stock Elevator

FIGS. 9 a and 9 b are side views of the tower pipe elevator 150 systemin use for J-Lay operation.

Quad lengths or double lengths of pipe 15010 are transported to the topof the tower for welding to the pipe string held within the moonpool bythe lower tower clamp 210. To achieve this, a pipe stock elevator systemis provided on the starboard side leg of the tower.

FIG. 9 a shows the pipe stock elevator system preparing to receive a newsection of pipe. Deck mounted walking beams are used to move fabricatedquad lengths or double lengths of pipe onto a deck mounted “strong back”15020. The pipe is secured to the strong back using hydraulic clamps15022 and the strong back 15020 is connected to a deck mounted pivotpoint aft 15030 of the starboard side tower leg. A wire 10642, fed froma winch 1064 located on the top starboard side of the tower and mountedadjacent the pipe alignment tool 142, is attached to the aft end of thepipe strongback and is used to pull the pipe and strongback assembly15020 to a position parallel to the starboard side tower leg. Toaccommodate tower deployment angles of between 60° and 90° from thehorizontal, lateral compliance is provided in the position of the deckmounted pivot point 15030.

Attached to the starboard side tower leg is a hinged frame 152 whichhouses upper pipe alignment clamp 15210 and lower pipe alignment clamps15220. As the pipe elevator system 150 is raised to its positionparallel to the starboard side tower leg, the pipe mates with and isgripped by the upper and lower pipe alignment clamps 15210, 15220. Oncefully gripped by the alignment clamps, the clamps 15022 on thestrongback release their grip on the pipe and the strongback is loweredback down to deck level to accept the next length of pipe. The pipealignment clamp frame 152, complete with pipe 15020, is then rotatedinto position above the suspended catenary pipe 15012 within themoonpool.

FIG. 9 b illustrates the translation of a length of pipe from the deck102 to its location in the tower 106, clamped by the upper clamp 220,and awaiting insertion of the pipe alignment tool 1420 and subsequentwelding.

A garage 142, located at the top of the tower, houses a Serimer internalpipe alignment tool 1420 and its umbilical winch 1422 to supply all thenecessary services for internal pipe clamping and Argon gas shielding.

With the pipe swung into location, the internal pipe alignment tool 1420is lowered down the new pipe 15010 to partially emerge at the lower endof the pipe. The lower alignment clamp 15220 provides centralisation andthe upper alignment clamp 15210 provides rotation and movement in the x,y and z directions. These clamps, in conjunction with the internal pipealignment tool 1420, provide the necessary adjustments to enable the newpipe 15010 to be lined up with the previously welded pipe 15012.

Once the two pipes have been fully lined up with each other, a Serimerautomatic welding head is clamped to the outside of the pipes to carryout the circumferential weld to join the two pipes together. The weldingis carried out from a workstation 10680 located on top of the lowertower clamp 210. To optimise its position relative to the weld, theworkstation is able to move independently from the lower clamp in thevertical direction, forward/aft and in attitude to accommodate thevarious tower angles, as shown in more detail FIG. 10.

Pre welded joint lengths for J-lay and for RFW rigid reel manufactureare loaded onboard using the vessel cranes. Once onboard, the pipelengths are moved around the deck using deck craneage and pipe conveyorsystems.

Pipe Bending and Straightening System

Rigid Pipe product is deployed from the pipelaying vessel in three ways,namely

-   -   From a Firing Line, 112, 114, 116 with the product manufactured        into a continuous length on the vessel.    -   From a Carousel reels 1040, 170, or basket 1042, where the        product has been prefabricated at a remote site and then taken        onboard and stored on the vessel, or has been fabricated by a        firing line.    -   From a J-lay system, where up to quad joint lengths of pipe are        manufactured onboard and then introduced into the water in up to        quad lengths.

Both the Firing Line 112, 114, 116 and the Carousel 104 methods requirethe use of a Pipe Bending and Straightening System to allow the productto initially be stored and finally to be deployed with no bends in thepipe. The bending of rigid pipe is undertaken under a controlled tensionaround set radius structures and is then straightened before being bentinto another plane by pipe straighteners. The bends are performed aboutdistinct planes to minimise strain damage to the pipe as a result.

The method of manufacture and method of deployment of the pipe from thevessel determines the pipe routing on the vessel and hence how many bendand straightening operations are required. Tests have shown that thegreatest amount of strain damage is caused by the first bend made on apipe; thereafter subsequent bends are less damaging. The configurationof the apparatus on the vessel has been selected to ensure that thefirst bend performed on a straight pipe, be it directly manufactured onboard by a firing line, or loaded onto the carousel via the stinger,occurs around the radius controller with the largest radius. This isachieved by performing the first bend using the large radius controller128, at the front of the vessel.

The following Figures illustrate the route of products during theconstruction and deployment modes, as well as indicating the producthandling and bending equipment required to achieve each process.

-   -   FIG. 10—Deployment of onboard welded rigid product, from either        the manual firing line 114, 116 or from the RFW machine 112,        directly overboard through the deployment tower 106.    -   FIG. 11—Deployment of stored rigid product from the Carousel        104, produced from either the manual firing line 114, 116 or        from the RFW machine 112, directly overboard through the        deployment tower 106.    -   FIG. 12—Loading or deployment of rigid/flexible product onto the        Carousel 104 from the loading/deployment stinger 110.    -   FIG. 13—Deployment of rigid/flexible product, loaded from the        loading/deployment stinger, from the Carousel 104 overboard via        the deployment tower 106.    -   FIG. 14—Deployment of onboard welded rigid product, from either        the manual firing line 114, 116 or from the RFW machine 112,        onto the Carousel 104.    -   FIG. 15—Loading of flexible/umbilical product into the Carousel        Basket 1042 from the loading/deployment stinger 110.    -   FIG. 16—Deployment of flexible/umbilical product from the        Carousel Basket 1042 to the deployment tower 106.

When manufacturing the pipe using the Firing Line technique the pipe ismanufactured on the port side of the vessel by continuously adding pipelengths onto one another. As each length is added the pipe is pulledaround a series of radius controller 128 and pipe straightener 118, 119combinations before being deployed to seabed using the Deployment TowerClamping System 210, 220 et al. The completed product can also bespooled directly onto the Carousel 104 for storage and later deployment.A predetermined back tension is maintained on the pipe at all times byusing a pipe tensioner 125 located before the first bend radiuscontroller 128, as illustrated in FIG. 10.

During direct lay operations as illustrated in FIG. 10, the route takenby the product passes through the following apparatus:-

-   -   A 22 m radius wall 128. This wall directs the pipe from the port        side of the vessel to the starboard side and the pipe is        supported in a conveyor arrangement that will reduce the risk of        buckling of the pipe during the bending operation. The elevation        of the conveyor arrangement is fixed for all operations.    -   A first pipe straightener 118. This straightener is located        immediately after the pipe exits from the 22 m radius wall and        will remove the bend introduced in the pipe from passing the        wall. The straightener is mounted on a pivotable table (not        shown) that alters its angle to match the angle of attack of the        pipe being deployed, although for direct lay operations the        angle will be substantially horizontal.    -   A 24 m radius Vertical Radius Bend Controller 136, as shown in a        detailed side view in FIG. 17. This item of equipment is used to        direct the pipe to the Deployment Arch 140 located on the        Deployment Tower 106. This item will also utilise conveyor        segments 13625 to support the pipe as it passes to reduce the        opportunity for buckling. The Vertical Bend Radius Controller        136 is mounted on a platform 13630 capable of being positioned        laterally along the platform to accommodate the tower position        when the tower is angled between the 60 and 90 degree positions.        The Vertical Radius Bend Controller is a passive unit and no        back tension control is applied at the unit.    -   A second pipe straightener 119. This pipe straightener is used        to remove the bend introduced in the Vertical Radius Bend        Controller 136 and the straightener is pivotably mounted on to        the top of the Vertical Radius Bend Controller. The Straightener        angle is adjusted to match the pipe angle throughout the        associated Tower angle range. The skilled person will appreciate        that instead of using the straightener alone to direct the        straightened pipe at the appropriate angle, either or both of        the Vertical Radius Bend Controller and straightener may be        pivotable to perform the same function.    -   A Tower Radius Control Arch 140. This arch provides a 12 m        radiused bend controller that accepts the pipe from the Vertical        Radius Bend Controller 136 and directs the pipe to the        Deployment Clamps 210, 220 located in the tower 106, again        conveyor sections are used on the arch. As the Arch is mounted        on the Tower any change in angle of the Tower will change the        angle at which the Arch operates.    -   A third pipe straightener 120. This pipe straightener is used to        remove the bend introduced in the Tower Radius Control Arch 140        and the straightener is mounted upon the arch, in line with the        deployment line extending through the Pipe Deployment Clamps        210,220. The third straightener 120 can be moved out the way, so        as not to interfere with J-lay of rigid sections of pipe.

When using the Carousel 104 in the system pipe must first be stored onthe Carousel. Pipe is either loaded from the stinger 110 (FIG. 12) orfrom the firing line 112, 114, 116 on the port side (both Serimer 114,116 and RFW 112 produced welds) (FIG. 14).

FIG. 12 illustrates pipe being produced at a location remote from theship (for example, either a shore base facility or from “wet storage” onthe seabed), whereby the lengths are recovered up the loading stinger110 and then wrapped onto the Carousel reel 1040 by passing around anoff-spooling arm 134. A tensioner 124 mounted on the elevating platformlocated adjacent to the Carousel 104 is used to provide the holdbacktension required during spooling operations. Tie-in welds 11010 (joiningthe two sections together) are completed on an elevating platform beforecontinuing with the next pipe section recovery operation. When the endof the product is brought onboard, a hold back winch is connected to theproduct and tensioned prior to opening the tensioner for final storageon the carousel. The illustrated straightener 118 is not required forloading operations, but is used to straighten the pipe when deployingfrom the reel.

FIG. 14 illustrates long pipe lengths being produced onboard by a firingline 112, 114, 116 and their subsequent loading onto the Carousel reel1040 by passing around the outer wall 128 to the starboard side andspooling onto the Carousel reel 1040, in a wrap direction opposite tothat for stinger-loaded product.

When deploying pipe from the Carousel 104, as illustrated in FIG. 11 thepipe is routed off the Carousel, and:-

-   -   Around the Offloading Arm 130. The Offloading arm 130 is a        pivoting large radius arm which is used to direct the pipe from        the Carousel reel 1040 to a common deployment line on either        side of the vessel. The arm pivots relative to the Carousel to        take account of the amount of pipe stored on the Carousel.    -   Through a first pipe straightener 118. This straightener is        located immediately after the pipe exits from the Offloading        Wall 128 and will remove the bend introduced in the pipe from        being stored on the Carousel and in passing the Offloading Arm        130. The straightener is mounted on a pivotable table (not        shown) that alters its angle to match the angle of attack of the        pipe being deployed, as it unspools. The long distance between        the point of the product being unspooled and the straightener        (the path between the tip of the arm, and the whole of the        offloading wall 128, marked as “B”, “C” and “D” on FIG. 4 a)        negates the requirement for some arrangement for matching the        height of the pipe train to the product as it is being        unspooled. The pivoting first pipe straightener and long path        length achieve the same function, in a more simple manner.    -   Through the Vertical Radius Bend Controller 138. The Vertical        Bend Radius Controller 136 is mounted on a platform 13630        capable of being positioned laterally along the platform to        accommodate the tower position when the tower is angled between        the 60 and 90 degree positions. The Vertical Radius Bend        Controller is a passive unit and no back tension control is        applied at the unit. All back tension is controlled at the        Carousel.    -   A second pipe straightener 119. This pipe straightener is used        to remove the bend introduced in the Vertical Radius Bend        Controller 138 and the straightener is mounted on to the top of        the Vertical Radius Bend Controller. The Straightener angle can        be adjusted to match the pipe angle throughout the associated        Tower angle range. The skilled person will appreciate that        instead of using the straightener alone to direct the        straightened pipe at the appropriate angle, either or both of        the Vertical Radius Bend Controller and straightener may be        pivotable to perform the same function.    -   A Tower Radius Control Arch 140. This arch provides a 12 m        radiused bend controller that accepts the pipe from the Vertical        Radius Bend Controller and directs the pipe to the Deployment        Clamps 210, 220 located in the tower, again conveyor sections        are used on the arch. As the Arch is mounted on the Tower any        change in angle of the Tower will change the angle at which the        Arch operates.    -   A third pipe straightener 120. This pipe straightener is used to        remove the bend introduced in the Tower Radius Control Arch 140        and the straightener is mounted upon the arch, in line with the        deployment line extending through the Pipe Deployment Clamps        210,220. The third straightener 120 can be moved out the way, so        as not to interfere with J-lay of rigid sections of pipe.

Flexible product is installed onto the Carousel in the same manner orcan be delivered to the vessel on reels 170. Flexible product isdeployed from the vessel using the Flexible Product Platform.

FIG. 15 illustrates loading of Flexibles and Umbilicals into theCarousel basket 1042 where the Carousel Basket Drive Motors 10412 aredriven to provide rotational power to the basket.

Flexibles and Umbilicals are loaded into the carousel basket 1042 viathe loading stinger 110 from either a shore base facility or from asupply boat at sea. In each case the product is routed up the stinger110, through the tensioner 124, over the manipulator arm 180 and intothe basket 1042. As the tensioner hauls the product up the stinger, thecarousel is rotated and the manipulator arm driven to lay the productinto the basket in as space-effective a manner as possible.

FIG. 17 shows the Vertical Radius Bend Controller 136, 138 in furtherdetail. The associated straightener 119 is arranged on a pivot 13610 anddriven by a hydraulic ram 13620 to facilitate the different angles thatthe tower 106 can be set at. Such an arrangement negates having to alterthe pitch of the vertical radius controller 136, 138 with respect to thetilt of the tower. The pitch of the straightener 119 is adjusted tomatch the angle of the product as it passes down the tower. Furthermore,the longitudinal position of the vertical radius controller is varied tomatch the effective translation of the point of product on which thestraightener acts, with respect to the deck of the vessel.

The third deployment system for rigid pipe product, where sections arewelded together for J-lay, has been previously described under thesection entitled “Pipe Stock Elevator”.

Abandoment and Recovery

FIGS. 18 a, 18 b and 18 c show the Abandonment and Recovery (A&R) system230 in side and plan views, configured for deep and shallow A&Ractivities.

The A&R equipment comprises a fully heave compensated deep waterlowering system, rated to 1000 tonnes working load, and a productinitiation winch 23010, rated to 300 tonnes working load.

The deep A&R system can also be used to lower a specified 600 tonnesdeck package to the seabed, in a fully heave compensated manner, whilstthe initiation winch 23010 can also be used as a shallow A&R winch.

The deep A&R system (FIG. 18 a) comprises an individual storage reel23020 and a dolly base 23022 located on the aft side of the moonpool foruse in conjunction with the tower's two moving clamps. The storage reelis normally stored on the dolly base and holds 3000 metres of 160 mm OD,spiral wound, 2,500 tonnes minimum breaking load wire.

To use the deep A&R system for deploying product to the seabed, theproduct is held within the tower using the lower moving clamp 210. Amessenger wire from a deck mounted utility tugger is routed from themoonpool area, up through the upper moving clamp 220, over a sheave23030 at the top of the tower and down to the deck adjacent to the A&Rdolly base. The messenger wire is then connected to the open speltersocket at the end of the A&R wire 23040 and the utility winch is used topull the A&R wire back through the system to allow the connection of theA&R wire to the product. With the upper clamp 220 gripping the A&R wire23040, the clamp is then raised to take the full catenary load to unloadthe lower clamp 210. Under a no load condition, the lower clamp releasesits grip on the product to allow the upper clamp 220 to start loweringthe product through the moonpool. The upper and lower moving clamps willthen work together, alternately gripping the A&R wire 23040, to lowerthe product to the seabed.

Structures of up to 600 tonnes can also be deployed to the seabed usingthe deep A&R system in conjunction with a deck mounted over boardingcrane 160. Prior to overboarding the structure, a messenger wire isrouted from the aft deck, over the side of the vessel and up through themoonpool for connection to the open spelter socket on the end of thedeep A&R wire 23040. The messenger wire winch then pulls the deep A&Rwire down through the moonpool and up onto the aft deck for connectionto the structure. As the deck crane 160 overboards the structure andlowers it into the water, the A&R wire is also paid out using the towerclamps 210, 220. At an appropriate depth below the vessel, the load istransferred from the crane wire to the A&R wire and the crane wiredisconnected from the structure using either an acoustic shackle or anROV. The heave compensated deep A&R system is then used to lower thestructure to the sea bed where the wire is disconnected by either asecond acoustic shackle or an ROV.

FIG. 18 c illustrates the product initiation winch and shallow A&Rsystem, comprising skid mounted storage drum 23050, traction winch 23060and A-frame mounted sheave located on an extension to the existing maindeck on the forward side of the moonpool. Two deck mounted horizontaldeflection sheaves 23070, located forward of the skid and underneath thecarousel, route the wire from the storage drum onto the winch.

To use the initiation winch in product pull through mode, a messengerwire is routed around the system for connection to the wire on thewinch. The messenger wire pulls the initiation wire from the winch,around the extended A-frame mounted sheave, through the lower and upperclamp 210, 220, around the tower radius controller arch 140 and downaround the deck mounted vertical radius controller 136, 138 forconnection to the product on the carousel 104. The messenger wire isthen disconnected, the winch wire connected to the product and thetraction winch 23060 is used to pull the product through the system.Once through the lower clamp 210, the lower clamp grips the product andthe winch wire is disconnected. The upper and lower tower clamps 210,220 then work together, in a hand to hand mode, to lower the product tothe sea bed.

The initiation winch 23060 can also be used in the shallow A&R mode. Inthis mode, the winch wire is routed from the traction winch, around theretracted skid mounted A-frame sheave, up and over the sheave mounted atthe top of the tower, through the upper clamp 220 and down forconnection to the product held by the lower clamp 210. With the catenaryload taken by the winch, the lower clamp is opened under a no loadcondition and the winch is used to lower the product to the seabed.

As an alternative to using moving clamps to grip a rope for the deep A&Rsystem, a conventional 1000 tonnes A&R winch could be used.

Control System

It is essential that all products are loaded and deployed in acontrolled fashion and the lay operation is integrated with the shippositioning and movements.

There is provided a flexible and expandable, Integrated Control System(ICS) for the lay equipment. The system is used to control all of thepipelay and RFW processes. The ICS solution offers a robust and reliablearchitecture, extensive inherent functionality and advanced programminglanguages.

The control system is developed around the following architecture:

-   -   Fieldbus interface, (for example Profibus™).    -   Redundant Controllers.    -   Redundant Control Network.    -   Dedicated high performance motion controllers for the demanding        motion control requirements.    -   Global, scaleable open database.

The system is capable of simple expansion, simple to use integrationtools and advanced programming languages. The Profibus™ interface isused to communicate with remote I/O, motion controllers and other thirdparty sensors, such as encoders and MCC devices. Redundant controllersand a redundant network provide an increased level of reliability,whereby a dual failure of power supply, network or controller isrequired to render the system inoperable.

The dynamic performance requirements of many of the machine movementsrequire fast, accurate and complex control algorithms. This is achievedby using dedicated motion controllers and servo amplifiers. Thisfunctionality may be provided by using UnidriveSP™ or Unidrive™ devicesfor the electrical drives and Bosch Rexroth HNC™ devices for thehydraulic servo valves.

The operator interface is provided by dual headed operator workstationswhereby the pipelay and RFW processes are controlled and monitored. Anadvanced alarm management system is used to alert the operator toabnormal situations and provide advice on fault diagnosis. Ahierarchical display structure allows easy navigation around the variousdisplays that are grouped by function eg. RFW, Pipe Loading, Post WeldOperations, Pipelay etc.

Engineering and maintenance displays are also provided within the systemaccessed via password protected environments. Workstation locations areas a minimum located at the RFW, Deployment Tower and on the Bridge.

Quality management information is recorded and tracked by the ICS. Anexternal individual data logger is used to gather data during thewelding operations and transferred to the ICS for analysis and storage.Thus, the quality information for each weld and pipelay operation isstored centrally within the ICS. Backup and long term storage, archiveand retrieval facilities are also provided.

An advanced simulation package is provided. This thoroughly tests allI/O, graphical interfaces, alarming and sequences off-line away from thetarget hardware. The simulation can also be used in conjunction with aduplicated operator interface, to provide extensive operator training.

The existing vessels control system does not require amendment, howevera link to the vessels Integrated Computer Management System is provided.This link will be established under a ‘request permission’ mode that canbe removed at any time by a bridge command. This means that operationson the product lay control system can be performed remotely from thevessel system.

Safety interlocks are provided for safety critical functions andimplemented using either hardwired interlocks or a dedicated safetycritical PLC.

Further Embodiments

FIGS. 19 a and 19 b show a side elevation and plan view respectively ofalternative configurations of key components of the vessel.

A forward-leaning tower 400 is used for product deployment. Product ishandled mid-line to the ship.

As an alternative to a nested carousel, an independently driven twinspool carousel is adopted. An upper spool 410 is used for rigid pipelay,and an independently driven lower spool 412 for flexible product. Theskilled person will appreciate that the relative sizes of the two spoolsmay be different, according to the activities the vessel is beingdesigned for. Furthermore, three spools may be employed, the top two forexample being driven together, independently from the lower spool. Thetop spool could be used for shallow-water A&R operations, for example.

A product deployment manipulator arm 420 is used to extract product fromthe lower spool 412. A small horizontal radius controller 430 is used toensure the product is fed squarely into a tensioner 440, which is usedto grip the product, and lower it into the sea at a controlled rate. Aradius control wheel 450 is used to translate the product from asubstantially horizontal plane to a vertical plane for feeding into thesea via the moonpool.

The forward-leaning tower 400 is shown in a retracted position duringdeployment from the lower spool.

FIG. 19 b also shows a side-mounted product loading manipulator arm 460,which is used for loading the lower spool with product.

FIG. 20 a and 20 b are a more detailed side and plan view respectivelyof the vessel of FIGS. 19 a and 19 b, and where the upper spool 410 isbeing used to deploy rigid product.

Rigid product is unspooled from the upper spool 410, and drawn past ahorizontal radius controller 470 and through a first straightener 480 toensure the product is fed squarely and as a straight pipe into avertical radius controller 490. The product is bent in a controlledfashion by the vertical radius controller and is directed upwards andtowards a tower-mounted driven wheel 500, around which the productpasses. The product is redirected substantially 180° by the wheel, andpassed through a second straightener 510, before being directeddownwards into the moonpool 520. As with the previous configuration, aroller box (not shown) is used at the base of the tower, to maintain theproduct within the deployment centre line.

The horizontal radius controller 470, first straightener 480, verticalradius controller 490, product deployment manipulator arm 420, smallhorizontal radius controller 430, tensioner 440 and radius control wheel450 are located upon an elevating platform 530. The tower is raised orlowered to match the unspooling of rigid product from the upper spool.

FIGS. 19 b and 20 b also show a side-mounted platform/tensioner 540 forspool loading. Rigid product is loaded onto the spool by passing theproduct through the apparatus, which provides back tension to ensure theproduct is tightly wound onto the spool, and also provides horizontaland vertical translation to match the spooling height and width.

FIGS. 21 a and 21 b are a side and plan view respectively of differentarrangement for unspooling product from a rotating carousel.

A pipe or umbilical is discharged via a pipe conditioning train 1200,which comprises 1) a horizontal radius controller 1210 operating in thesame horizontal plane as the carousel 1130 such that it applies areverse curvature of constant radius, 2) a straightener 1120 forstraightening the pipe as it exits the horizontal radius controller, 3)a tracked tensioner 1230 for drawing the pipeline off the carousel andfeeding it through the rest the pipe conditioning train 1200 and beyond,and 4) a first vertical radius controller 1235 that by bending directsthe pipe from the horizontal plane up towards the top vertical radiuscontroller 1240 and straightener 1252 of a stem-mounted pipelay ramp1250.

The pipelay ramp 1250 is of conventional design, and comprises at itstop a second vertical radius controller 1240 which takes the pipelinefrom the pipe conditioning train 1200 and directs it into the sea bybending and subsequently straightening. The illustrated stem lay ramp1250 is similar to that used for the known vessel “Seaway Falcon”, andis adjustable to vary its position with respect to the stem of thevessel and the pipelaying method being adopted, such as S-Lay or J-Lay.On the ramp, the pipe is bent and straightened before passing through atensioner, moving clamp system, or other means for holding the weight ofthe catenary of pipe between the ship and the seabed. The rampillustrated could equally well be mounted over a moonpool, according tothe configuration of the pipe laying apparatus upon the vessel.

The whole pipe conditioning train 1200 is mounted upon a lift 1260 thatcan be raised and lowered, thereby allowing adjustment of the verticalalignment of the first horizontal radius controller 1210 with respect tothe carousel. This facility is used to avoid riding turns or excessivegaps between successive turns during unspooling (or spooling, whereapplicable) of the carousel 1134. A portion 1262 of the deck is not partof the lift. The boundaries of the lift are shown in the plan views(FIGS. 21 b and 22 b) of the vessel.

FIGS. 22 a and 22 b are zoomed side and plan view respectively of thelift-mounted apparatus in the vessel of FIGS. 21 a and 21 b.

The lift 1260 supporting the pipe conditioning train 1200 is recessedinto the shelterdeck with its drive mechanism beneath the deck. Theoperational range of the lift provides translation in the vertical planebetween the bottom and top surfaces of the carousel 1134. The skilledperson will appreciate that any alternative form of adjusting the heightof the lift could be used, such as screw jacks or electromagneticactuators.

The side view, FIG. 22 a, shows the “Caterpillarm” track 1320 of thehorizontal radius controller 1210. This can be more clearly seen in theplan view, FIG. 22 b, where a continuous track is looped and tensionedto retain a preset radius 1330. The radius controller is dimensioned toaccommodate all anticipated angles of entry from the reel as the pipeunwinds from a full reel to an empty one. The horizontal radiuscontroller is pivotably moveable about pivot 1340, to ensure that forall angles of entry the pipe is always smoothly guided into thestraightener 1220.

1. A sea-going vessel having pipe launching apparatus for layingcontinuous elongate product, the pipe launching apparatus comprising:first product supply apparatus arranged substantially at deck level forsupplying continuous elongate product into a first path along a deck atone side of the vessel; second product supply apparatus arrangedsubstantially at deck level for supplying continuous elongate productinto a second path along deck at the opposite side of the vessel; atower structure mounted substantially on the vessel centreline andinclinable to a desired launch angle to align with a catenary curve ofsaid product suspended below the vessel; pipe handling means within saidtower structure operable to receive said product at a central elevatedposition for gripping and supporting the weight of the suspended productwhile paying it out; and tower diverter means operable for receivingsaid product from deck level at one of two side elevated positions abovesaid first path or said second path respectively according to whicheverproduction apparatus is being used, and for supporting the product in acurved path from the side elevated position to said central elevatedposition and aligning it with said launch angle.
 2. A sea-going vesselas claimed in claim 1, wherein said first product supply apparatusincludes at least one pipeline production facility for receivingsections of rigid pipe and joining them to produce said continuousproduct for supply directly to said pipe handling means via said firstpath.
 3. A sea-going vessel as claimed in claim 2, wherein analternative production facility for a different process is arranged inparallel, on a deck above the other.
 4. A sea-going vessel as claimed inclaims 2 or 3, wherein said pipeline production facility is arrangedtoward the opposite side of the vessel from said first path andanti-parallel thereto, the product being diverted through a 180° curvedpath into said first path and thence to the tower diverter.
 5. Asea-going vessel as claimed in claim 4, wherein said second productsupply apparatus includes the same pipeline production facility operableto supply continuous product onto a storage carousel via substantiallythe same curved path in a first phase of operation and then in a secondphase of operation to unload the stored product via said 180° curvedpath substantially in reverse and thus into said second path and thenceto the tower diverter.
 6. A sea-going vessel as claimed in claim 4,wherein said 180° curved path is defined by a diverter structurepartially surrounding said carousel.
 7. A sea-going vessel as claimed inclaim, wherein said first product supply apparatus includes a horizontalpipe storage carousel for storing a length of pre-fabricated continuousproduct, the carousel being operable to unload said product into saidfirst path and thence to the tower diverter.
 8. A sea-going vessel asclaimed in claim 7, wherein said carousel is operable as part of saidfirst product supply apparatus and as part of said second product supplyapparatus, according to its direction of rotation during unloading.
 9. Asea-going vessel as claimed in claim 8, wherein said carousel isarranged to be loadable from an on-board pipeline production facilityand alternatively from an off-board supply, the direction of rotationduring unloading being different according to the source of supply. 10.A sea-going vessel as claimed in claim 9, wherein a loading stinger isprovided on the vessel for receiving pipe from said off-board supply.11. A sea-going vessel as claimed in claim 7, wherein said carousel issubstantially surrounded by a large radius diverter structure, theproduct being diverted from storage on the carousel around the outsideof this structure whether serving as part of the first or secondproduction apparatus.
 12. A sea-going vessel as claimed in claim,wherein said pipe launching apparatus further includes first and secondvertical radius controllers mounted at deck level for receiving theproduct and diverting the product upward from said first path and saidsecond path respectively toward said tower diverter means.
 13. Asea-going vessel as claimed in claim 12, wherein said first and secondvertical radius controllers include common components, these beingtransferable from the one side of the vessel to the other side of thevessel according to which production apparatus is being used.
 14. Asea-going vessel as claimed in claim 12, wherein said first and secondvertical radius controllers are mounted for fore-and-aft movement toadjust their position according to the inclination of the towerstructure.
 15. A sea-going vessel as claimed in claim 12, wherein saidpipe launching apparatus further comprises a straightener associatedwith each vertical radius controller for removing a plastic bendingintroduced by the vertical radius controllers.
 16. A sea-going vessel asclaimed in claim 15, wherein said straightener is mounted on a pivotingarm adjustable according to the inclination of the tower structure. 17.A sea-going vessel as claimed in claim, wherein said tower divertermeans comprises a radius controller mounted on the tower above saidelevated position and movable between port and starboard operatingpositions for receiving said product at a side elevated position abovewhichever of said first path or said second path is appropriate.
 18. Asea-going vessel as claimed in claim 17, wherein said radius controlleris movable between said port and starboard positions by swinging it inan arc about a lay axis of the pipe handling means.
 19. A sea-goingvessel as claimed in claims 18 or 19, wherein said tower diverter meansfurther comprises a straightener supported so as to move together withthe radius controller.
 20. A sea-going vessel as claimed in any of claim17, wherein said radius controller is further operable at a centralposition for receiving elongate article from a central product supplyapparatus at deck level. 21-104. (canceled)